fix: prevent underflow crash in truncate_str (#125)

jordond · web-flow · commit 395c5000de4e · 2026-01-23T12:23:43.000-05:00
diff --git a/cli/src/commands/history.rs b/cli/src/commands/history.rs
@@ -4,6 +4,7 @@ use color_eyre::eyre::Result;
 
 use crate::cli::HistoryCommands;
 use crate::data::{self, HistoryStore};
+use crate::ui::utils::truncate_str;
 
 pub fn run(command: Option<HistoryCommands>) -> Result<()> {
     let cmd = command.unwrap_or(HistoryCommands::Summary {
@@ -218,14 +219,6 @@ pub fn get_date_range(period: &str) -> (String, String) {
     }
 }
 
-pub fn truncate_str(s: &str, max_len: usize) -> String {
-    if s.len() <= max_len {
-        s.to_string()
-    } else {
-        format!("{}...", &s[..max_len - 3])
-    }
-}
-
 fn export_to_json(
     from: &str,
     to: &str,
diff --git a/cli/src/main.rs b/cli/src/main.rs
@@ -68,7 +68,8 @@ mod tests {
     use clap::CommandFactory;
 
     use crate::cli::{DaemonCommands, HistoryCommands, ThemeCommands};
-    use crate::commands::history::{escape_csv, get_date_range, truncate_str};
+    use crate::commands::history::{escape_csv, get_date_range};
+    use crate::ui::utils::truncate_str;
 
     #[test]
     fn cli_configuration_is_valid() {
diff --git a/cli/src/ui/history.rs b/cli/src/ui/history.rs
@@ -15,7 +15,7 @@ use crate::input::keys;
 use crate::theme::ThemeColors;
 
 use super::utils::{
-    centered_rect_percent, energy_unit_label, format_energy, format_energy_compact,
+    centered_rect_percent, energy_unit_label, format_energy, format_energy_compact, truncate_str,
 };
 
 pub fn render(frame: &mut Frame, app: &App, theme: &ThemeColors) {
@@ -453,7 +453,7 @@ fn render_top_processes(frame: &mut Frame, area: Rect, app: &App, theme: &ThemeC
             let power_color = power_level_color(p.avg_power, max_power, theme);
 
             Row::new(vec![
-                truncate_name(&p.process_name, name_width),
+                truncate_str(&p.process_name, name_width),
                 format!("{:.1}", p.avg_power),
                 format_energy_compact(p.total_energy_wh, energy_unit),
                 format!("{:.0}", p.avg_cpu),
@@ -509,11 +509,3 @@ fn render_footer(frame: &mut Frame, area: Rect, theme: &ThemeColors) {
     .centered();
     frame.render_widget(footer, area);
 }
-
-fn truncate_name(name: &str, max_len: usize) -> String {
-    if name.len() <= max_len {
-        name.to_string()
-    } else {
-        format!("{}...", &name[..max_len - 3])
-    }
-}
diff --git a/cli/src/ui/mod.rs b/cli/src/ui/mod.rs
@@ -11,7 +11,7 @@ mod status_bar;
 mod system_stats;
 mod theme_importer;
 mod theme_picker;
-mod utils;
+pub mod utils;
 
 use ratatui::{
     layout::{Constraint, Direction, Layout},
diff --git a/cli/src/ui/processes.rs b/cli/src/ui/processes.rs
@@ -10,7 +10,7 @@ use crate::app::{App, SortColumn};
 use crate::data::ProcessState;
 use crate::theme::ThemeColors;
 
-use super::utils::format_duration;
+use super::utils::{format_duration, truncate_str};
 
 const COL_EXPAND: u16 = 6;
 const COL_PID: u16 = 7;
@@ -235,8 +235,8 @@ pub fn render(frame: &mut Frame, area: Rect, app: &mut App, theme: &ThemeColors)
                 Span::styled(process.pid.to_string(), style),
                 Span::styled(status_char, status_style),
                 Span::styled(format!("{:.1}", process.energy_impact), style),
-                Span::styled(truncate_name(display_name, name_width), style),
-                Span::styled(truncate_name(&process.command_args, command_width), style),
+                Span::styled(truncate_str(display_name, name_width), style),
+                Span::styled(truncate_str(&process.command_args, command_width), style),
                 Span::styled(format!("{:.1}", process.cpu_usage), style),
                 Span::styled(format_memory(process.memory_mb), style),
                 Span::styled(disk_io, style),
@@ -269,14 +269,6 @@ pub fn render(frame: &mut Frame, area: Rect, app: &mut App, theme: &ThemeColors)
     frame.render_widget(table, inner);
 }
 
-fn truncate_name(name: &str, max_len: usize) -> String {
-    if name.len() <= max_len {
-        name.to_string()
-    } else {
-        format!("{}...", &name[..max_len - 3])
-    }
-}
-
 fn format_header(name: &str, col: SortColumn, current: SortColumn, indicator: &str) -> String {
     if col == current {
         format!("{} {}", name, indicator)
diff --git a/cli/src/ui/status_bar.rs b/cli/src/ui/status_bar.rs
@@ -11,6 +11,8 @@ use crate::data::SystemInfo;
 use crate::input::keys;
 use crate::theme::ThemeColors;
 
+use super::utils::truncate_str;
+
 pub fn render_title_bar(
     frame: &mut Frame,
     area: Rect,
@@ -45,11 +47,7 @@ pub fn render_title_bar(
 
 pub fn render_status_bar(frame: &mut Frame, area: Rect, app: &App, theme: &ThemeColors) {
     let theme_name = app.config.theme_name();
-    let theme_display = if theme_name.len() > 12 {
-        format!("{}...", &theme_name[..9])
-    } else {
-        theme_name.to_string()
-    };
+    let theme_display = truncate_str(theme_name, 12);
 
     let appearance = app.config.appearance_label().to_lowercase();
 
diff --git a/cli/src/ui/utils.rs b/cli/src/ui/utils.rs
@@ -125,6 +125,19 @@ pub fn convert_temperature(celsius: f32, unit: TemperatureUnit) -> f32 {
     }
 }
 
+pub fn truncate_str(s: &str, max_len: usize) -> String {
+    let char_count = s.chars().count();
+    if char_count <= max_len {
+        s.to_string()
+    } else if max_len <= 3 {
+        s.chars().take(max_len).collect()
+    } else {
+        let visible_len = max_len - 3;
+        let result: String = s.chars().take(visible_len).collect();
+        result + "..."
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -241,4 +254,61 @@ mod tests {
             "1.0 GiB"
         );
     }
+
+    #[test]
+    fn test_truncate_str_no_underflow_when_max_len_small() {
+        assert_eq!(truncate_str("Terminal", 0), "");
+        assert_eq!(truncate_str("Terminal", 1), "T");
+        assert_eq!(truncate_str("Terminal", 2), "Te");
+        assert_eq!(truncate_str("Terminal", 3), "Ter");
+    }
+
+    #[test]
+    fn test_truncate_str_adds_ellipsis() {
+        assert_eq!(truncate_str("Terminal", 7), "Term...");
+        assert_eq!(truncate_str("Terminal", 4), "T...");
+    }
+
+    #[test]
+    fn test_truncate_str_unchanged_when_fits() {
+        assert_eq!(truncate_str("Terminal", 8), "Terminal");
+        assert_eq!(truncate_str("Terminal", 10), "Terminal");
+    }
+
+    #[test]
+    fn test_truncate_str_utf8_multibyte_chars() {
+        // Emoji (4 bytes each in UTF-8)
+        assert_eq!(truncate_str("🚀🔥💻", 3), "🚀🔥💻"); // Fits exactly
+        assert_eq!(truncate_str("🚀🔥💻", 2), "🚀🔥"); // max_len <= 3, no ellipsis
+        assert_eq!(truncate_str("🚀🔥💻🎉", 4), "🚀🔥💻🎉"); // Fits exactly (4 chars)
+        assert_eq!(truncate_str("🚀🔥💻🎉🌟", 4), "🚀..."); // Truncates with ellipsis
+
+        // Mixed ASCII and emoji
+        assert_eq!(truncate_str("Terminal🚀", 9), "Terminal🚀"); // Fits exactly
+        assert_eq!(truncate_str("Terminal🚀", 8), "Termi..."); // Truncates
+
+        // CJK characters (3 bytes each in UTF-8)
+        assert_eq!(truncate_str("文字列", 3), "文字列"); // Fits exactly
+        assert_eq!(truncate_str("文字列テスト", 5), "文字..."); // Truncates with ellipsis
+
+        // Accented characters
+        assert_eq!(truncate_str("café", 4), "café"); // Fits exactly
+        assert_eq!(truncate_str("naïve", 4), "n..."); // Truncates with ellipsis
+    }
+
+    #[test]
+    fn test_truncate_str_utf8_edge_cases() {
+        // Empty string
+        assert_eq!(truncate_str("", 0), "");
+        assert_eq!(truncate_str("", 5), "");
+
+        // Single multi-byte char with small max_len
+        assert_eq!(truncate_str("🚀", 1), "🚀"); // Fits (1 char)
+        assert_eq!(truncate_str("🚀", 0), ""); // Zero length
+
+        // Ensure no panic on boundary conditions
+        assert_eq!(truncate_str("🚀hello", 1), "🚀");
+        assert_eq!(truncate_str("🚀hello", 4), "🚀...");
+        assert_eq!(truncate_str("🚀hello", 6), "🚀hello");
+    }
 }
diff --git a/fixtures/responses/current_data.json b/fixtures/responses/current_data.json
@@ -34,6 +34,7 @@
         "pid": 1234,
         "name": "Safari",
         "command": "/Applications/Safari.app/Contents/MacOS/Safari",
+        "command_args": "/Applications/Safari.app/Contents/MacOS/Safari -NSDocumentRevisionsDebugMode YES",
         "cpu_usage": 15.5,
         "memory_mb": 256.0,
         "energy_impact": 25.0,
@@ -43,6 +44,7 @@
             "pid": 1235,
             "name": "Safari Web Content",
             "command": "Safari Web Content",
+            "command_args": "Safari Web Content",
             "cpu_usage": 5.0,
             "memory_mb": 128.0,
             "energy_impact": 10.0,
@@ -63,6 +65,28 @@
         "run_time_secs": 7200,
         "total_cpu_time_secs": 600
       }
-    ]
+    ],
+    "system": {
+      "chip": "Apple M1 Pro",
+      "os_version": "14.2.1",
+      "p_cores": 8,
+      "e_cores": 2
+    },
+    "system_stats": {
+      "cpu_usage_percent": 25.5,
+      "load_one": 2.5,
+      "load_five": 2.0,
+      "load_fifteen": 1.5,
+      "memory_used_bytes": 8589934592,
+      "memory_total_bytes": 17179869184,
+      "uptime_secs": 86400,
+      "is_warmed_up": true
+    },
+    "forecast": {
+      "duration_secs": 18000,
+      "avg_power_watts": 12.5,
+      "sample_count": 30,
+      "source": "daemon"
+    }
   }
 }
diff --git a/fixtures/responses/data_update.json b/fixtures/responses/data_update.json
@@ -34,6 +34,7 @@
         "pid": 1234,
         "name": "Safari",
         "command": "/Applications/Safari.app/Contents/MacOS/Safari",
+        "command_args": "/Applications/Safari.app/Contents/MacOS/Safari -NSDocumentRevisionsDebugMode YES",
         "cpu_usage": 15.5,
         "memory_mb": 256.0,
         "energy_impact": 25.0,
@@ -43,6 +44,7 @@
             "pid": 1235,
             "name": "Safari Web Content",
             "command": "Safari Web Content",
+            "command_args": "Safari Web Content",
             "cpu_usage": 5.0,
             "memory_mb": 128.0,
             "energy_impact": 10.0,
@@ -63,6 +65,28 @@
         "run_time_secs": 7200,
         "total_cpu_time_secs": 600
       }
-    ]
+    ],
+    "system": {
+      "chip": "Apple M1 Pro",
+      "os_version": "14.2.1",
+      "p_cores": 8,
+      "e_cores": 2
+    },
+    "system_stats": {
+      "cpu_usage_percent": 25.5,
+      "load_one": 2.5,
+      "load_five": 2.0,
+      "load_fifteen": 1.5,
+      "memory_used_bytes": 8589934592,
+      "memory_total_bytes": 17179869184,
+      "uptime_secs": 86400,
+      "is_warmed_up": true
+    },
+    "forecast": {
+      "duration_secs": 18000,
+      "avg_power_watts": 12.5,
+      "sample_count": 30,
+      "source": "daemon"
+    }
   }
 }
diff --git a/fixtures/responses/status.json b/fixtures/responses/status.json
@@ -8,7 +8,7 @@
     "version": "0.1.0",
     "subscriber_count": 2,
     "history_enabled": true,
-    "protocol_version": 1,
+    "protocol_version": 2,
     "min_supported_version": 1
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`"version": "0.1.0",`
`9`	`9`	`"subscriber_count": 2,`
`10`	`10`	`"history_enabled": true,`
`11`		`- "protocol_version": 1,`
	`11`	`+ "protocol_version": 2,`
`12`	`12`	`"min_supported_version": 1`
`13`	`13`	`}`
`14`	`14`	`}`